Admission control of emergency connections

ABSTRACT

The present invention relates to a solution for handling emergency or prioritized communication in a wireless communication network during negotiation of access to the wireless communication network from a mobile station using dedicated emergency multiple-access sequences which are also used as communication division codes in communication with a base station of the network.

TECHNICAL FIELD

The present invention relates to emergency or prioritized communicationin a telecommunications network and in particular to setting up acommunication link for emergency or prioritized communication.

BACKGROUND OF THE INVENTION

The setup of traffic connections for the air interface in a telecomsystem is traditionally handled by a specific node BSC for GSM, RNC forUMTS, and ASN-GW for an IEEE802.16/WiMAX network. The setup of a serviceis typically requested by a mobile station (MS) and signaled to anapplication server in the core network.

However in a loaded network, it may be difficult for the MS to getaccess to air interface resources even to request the setup of aservice. In case the service is needed for emergency purposes, i.e. 911there is a strong wish to be able to prioritize this request andminimize the latency for setup of such services.

The IEEE802.16 has support for different QoS, which can have differentpriority settings. However before a setup of a service is possible tomake the MS must be authenticated and admitted to the network.

Also as IEEE 802.16 is an OFDMA based system where all air interfaceresources are shared between users a mobile station (MS) may encounterproblems to be granted bandwidth to request the setup of a service ifthe air interface is fully utilized and as there today exist nopossibility to differentiate different users during initial ranging orbandwidth request.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to remedy at leastsome of the problems relating to known solutions. This is provided in anumber of aspects in which a first is a method of handling emergencycommunication between a mobile station, MS, and a base station, BS,comprising the steps of:

-   -   initiating an emergency communication link;    -   obtaining specific emergency communication establishment        sequences; using the specific emergency communication        establishment sequences during negotiation of access to the BS;    -   wherein the sequences are also used as communication division        codes.

Specific CDMA codes may be used to indicate emergency access.

The MS may send a second indication of emergency access in anidentification message.

Specific random access preamble sequences may be used to indicateemergency access.

The method may further comprise a step of receiving emergency sequencesfrom the BS.

The method may further comprise a step of reading stored pre setemergency sequences in the MS.

The step of obtaining emergency sequences may comprise a step ofchoosing the sequence randomly from a set of available emergencysequences.

The step of using the sequences during negotiation may be performedduring initial access establishment and/or during negotiation duringbandwidth establishment.

Another aspect of the present invention, a mobile station for a wirelesscommunication network is provided, comprising:

-   -   an transceiver for wireless communication with a base station,        i.e. BS;    -   a processor arranged to execute functions for:        -   initiating an emergency communication link;        -   obtaining specific emergency communication establishment            sequences;        -   using the specific emergency communication establishment            sequences during negotiation of access to the BS;    -   wherein the sequences are also used as communication division        codes.

Yet another aspect of the present invention, a base station is providedfor wireless communication with a mobile Station, i.e. MS, comprisingmeans for detecting communication establishment sequences, means foridentifying specific emergency sequences from the establishmentsequences, and means for handling emergency communication, wherein thesequences are also used as communication division codes.

Still another aspect of the present invention, a computer program isprovided for a mobile station, i.e. MS, comprising instruction sets for:

-   -   controlling wireless communication with a base station, i.e. BS;    -   initiating an emergency communication link;    -   obtaining specific emergency communication establishment        sequences;    -   using the specific emergency communication establishment        sequences during negotiation of access to the BS;    -   wherein the sequences are also used as communication division        codes.

Usage of standardized/specific multiple-access sequences only allowedfor emergency purposes are proposed to ensure priority of emergencysetups.

A specific parameter is suggested to be included for a number of callmanagement messages for fast detection of emergency calls and thus givethe base station (system) the possibility for prioritization of therequested traffic during admission control to the system.

Handling of emergency calls are enhanced as the probability ofsuccessful setup is increased, which is very much desired in atelecommunication system.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in a non-limiting wayand in more detail with reference to exemplary embodiments illustratedin the enclosed drawings, in which:

FIG. 1 illustrates schematically a network according to the presentinvention;

FIG. 2 illustrates schematically in a block diagram a flowchart of amethod according to the present invention;

FIG. 3 illustrates schematically a situation for two mobile stationsconnecting simultaneously to a base station according to the presentinvention;

FIG. 4 illustrates schematically in a block diagram a mobile deviceaccording to the present invention; and

FIG. 5 illustrates schematically in a block diagram an infrastructuredevice according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1 reference numeral 1 generally indicate a network configurationaccording to the present invention, comprising a base station BS) 5 orsimilar network access gateway for accessing from a mobile station (MS)(which can be any type of wireless terminal, including but not limitedto, e.g. a mobile phone, laptop, PDA (Personal Digital Assistant),security appliance, and so on) 2, 3 to a communication network 6. The MScommunicates wirelessly 4 with the BS 5 using any suitable protocol andradio link. The present invention addresses the problem when an MS triesto connect to a communication network under certain circumstances wherethere is a need to increase the probability to actually get aconnection: for instance when there is an emergency situation and thereis a need to communicate with an emergency organization 7 (e.g. police,fire brigade, and medical help), connection of alarm equipment, and/orsurveillance equipment to a central receiving facility 7. Thesecircumstances will be discussed further in this document.

The wireless link between the MS and the BS may be of any suitable typeinvolving some means for registration of the MS, including but notlimited to any version of IEEE 802.11, 802.15, 802.16, 802.20, and802.22 series of communication standards and variations thereof (e.g.WiFi, WiMAX, and Wibro), LTE (Long term evolution) in 3GPP, or similarcommunication systems. WiMAX has means for registering the MS using aranging function at early stages of connection establishment and in thatprocess using CDMA codes for random access and in LTE there is a RandomAccess (RA) preamble/response function used in establishment of the MS.In WiMAX specific ranging CDMA codes may be used for alerting thenetwork about the emergency and/or prioritized link and in LTE specificRA preamble sequences may have corresponding function. CDMA codes inWiMAX and preamble sequences in LTE are two examples of multiple-accesssequences. These multiple-access sequences may be orthogonal ornon-orthogonal as understood by the skilled person.

Multiple-access sequences are used to distinguish communication linksfrom each other when all users within a communication cell communicateon the same frequency range and encode information to be transmittedwith a pseudo-random digital sequence unique for each user in the cell(or unique for each thread set up; a user may have several threads openat the same time depending on communication configuration)

It should be noted that the communication link between the BS and thenetwork may be of any suitable kind including either a wired or wirelesslink. The link may use any suitable protocol depending on type and levelof layer (e.g. as indicated by the OSI model) as understood by theperson skilled in the art.

The BS may be alerted about the level of emergency or level of prioritydesired using different ways depending on type of connection, type ofcommunication protocol, and level of connection already established:

-   1. If the MS has not been connected yet, establishment sequences    specifically agreed upon as emergency sequences may be used.-   2. If the MS is connected but has not been granted bandwidth it may    also use emergency sequences.-   3. If connection and bandwidth has been negotiated about,    information elements in call management messages may be used to    alert the BS about the emergency connection.

An overall flowchart for handling of emergency calls according to thepresent invention is shown in FIG. 2:

-   201. A decision to connect to a service is taken in first step.-   202. It is checked if the MS is registered in the network.-   203. If it is registered it is checked if the MS has been granted    bandwidth.-   204. If it has been granted bandwidth call management messages with    emergency information elements are used.-   205. If the MS is not registered emergency random access operation    is used.-   206. If the MS is registered but has not yet been granted bandwidth,    emergency bandwidth request is used.

Each of the involved processes is described in the sections below.

MS Requests Setup of Emergency Call

When a user or a machine determines that there is a need forestablishing a contact with a receiving service, the MS is initiated toconnect to the network 6. Typically this is done by a user dialing 112,911, or some other emergency call number (depending on type of emergencyand/or country); however, the MS may be arranged to be informed aboutthe emergency number to be used where the connection is to beestablished). However, this could also be a connection from a machine ina system which is capable of automatically determining that a connectionis to be started, e.g. a by authorities and operators approvedsurveillance camera automatically requesting to start sending data orvideo upon an alarm or triggering event. The receiving service can be anemergency center 7 directing the call to suitable service needed(police, ambulance services and so on) or it may be a security centerreceiving for instance a distress alarm or burglar alarm signal.Similarly the receiving service may be part of a surveillance system forelderly or handicapped people, e.g. in relation to home care services,where the person under care can contact the home care system for generalhelp or help in a distress situation. There are today many solutionswhere an elderly or handicapped person has a personal alarm in the formof an arm wrist device with a distress call button. This arm wristdevice may be arranged to communicate with a distress call center usinga communication protocol compatible with the present invention.Similarly, surveillance cameras and similar devices may be arranged touse a communication protocol compatible with the present invention andarranged to transmit images to a central storage or handling center if atriggering event has occurred, for instance a motion detection event(internally in the camera as a software detector using the images or anexternal dedicated motion detector).

When pushing the call setup button or initiating the connection in anyother suitable manner, the MS will start to request the setup of atransport connection or activate a pre-setup connection to carry therequested service.

The MS can be in different states and will perform different operationsdepending on its current state in the system:

-   -   Normal/active registered in the system with active services.    -   Normal/active registered in the system with no active services    -   Idle and not registered or even belonging to the system. Idle in        this context is interpreted as not connected to the current BS.        The MS may be registered in a core network (or ASN-GW in the        WiMAX case).        MS is Registered in the System and has Granted UL Bandwidth.

This is a typical case if the terminal or device already is activeperforming other tasks, such as transferring data files etc. It may thenuse the already granted UL bandwidth for the request of an additionalservice for the emergency purpose.

In the IEEE802.16 this is typically done by sending a dynamic serviceflow addition request message (DSA-REQ). In this message a number ofparameters are set among these are QoS parameter set type, schedulingservice type and traffic priority. Depending on the previousauthentication of the user the operator may allow/set these parametersdifferently.

In the present invention a generic parameter (e.g. a TLV-codedinformation element in the IEEE802.16 standard), is added to controlcommunication, which may be optionally included to call managementmessages indicating that these are emergency related.

Examples of IEEE802.16 messages where an emergency parameter havebenefit are:

-   1. DSA-REQ/RSP-   2. DSC-REQ/RSP

The BS (system) may also use this information for prioritizing of thisconnection for further data transfer, i.e. enhancing the probability forthe specific communication data to be delivered to the final destinationand granting access to the network.

MS is Registered in the System but Need UL Bandwidth.

In this case the MS needs to perform random access in order to requestbandwidth (BW). To improve both the probability of a successful requestof BW as well as minimize the latency for grant of BW for ULtransmission it is proposed to have separate multiple-access sequencesallocated for BW-request for emergency purposes.

It may be relevant to add emergency parameters in any subsequentmanagement messages (e.g. DSA-REQ/RSP and DSC-REQ/RSP for IEEE802.16).

MS is not Registered in the System.

In this case the MS is not registered in a system. This can be due tolack of roaming agreement with a system (visited NW) where it hascoverage or due to admission control rejection from its own NW (fullnetwork). Specified multiple-access sequences also for initial randomaccess will then improve the setup of emergency connections as admissioncontrol functionality may be adjusted for this purpose.

The emergency parameter described earlier may be added to additionalIEEE802.16 messages used for network entry below:

-   1. RNG-REQ/RSP-   2. SBC-REQ/RSP-   3. PKM-REQ/RSP-   4. REG-REQ/RSP-   5. DSA-REQ/RSP

In this case authentication processes may be simplified or omitted andthe MS is allowed to enter the system.

Static or Dynamic Information Transfer of Emergency Sequences.

Two methods for determining specific multiple-access sequences for useare proposed.

-   1. Static specification by reserving a limited number of    multiple-access sequences in the standard. This method is very    simple and ensures simple interoperability between different    manufacturers and system vendors. The multiple-access sequences are    then known to the MS and stored in a memory of the MS.-   2. Dynamic specification by broadcast information. Two new groups of    multiple-access sequences for emergency initial random access and    emergency BW request are added to the specification and broadcasted    in a similar way as CDMA codes for initial ranging, BW request,    periodic ranging, and handover are signaled today for IEEE802.16.

By this method it is possible for the system to increase the number ofmultiple-access sequences for emergency purposes dynamically so that thecase when many MSs (wireless terminals, cameras, etc) need access to thesystem simultaneously may be taken care of without the collisionprobability being higher for emergency calls than for normal calls.

The system may by this method even be solely dedicated for authoritydevices for public safety purposes as no multiple-access sequences fornormal operation are sent.

The probability of successful reception is increased as the collisionrisk is decreased. FIG. 3 illustrates this situation; two mobilestations 2, 3 simultaneously try to connect to a common base station 5.Collision risk of UL BW request ranging can be reduced if dedicatedmultiple-access sequences are used solely for emergency purposes. Forinstance, if a first MS (A) 2 need to make an emergency BW request itmay use a sequence 4 different from a second MS (B) 3 sequence 4′ usedfor regular connection purposes. The probability for both MS A and MS Bis in need of an emergency connection is low. However, in order toreduce the problem of two MS doing emergency connection at the sametime, each MS may choose randomly an emergency sequence from a fixed setof available emergency sequences. This would reduce the risk of two MSat the same cell using the same emergency sequence and thus reduce therisk of collision. This may be used in any of the situations asdescribed in this document.

The present invention is used in connecting mobile stations 2, 3 duringemergency or other prioritized events. Such a mobile station 400 isshown in FIG. 4. The solution may be implemented in software run in aprocessing unit 401 and stored in a memory 402. Furthermore, the mobilestation may comprise an interface 403 for connecting the processing unit401 with other components of the mobile station as understood by theperson skilled in the art. Furthermore, the mobile station comprises acommunication interface 404 for wireless communication with the BS 5.The processing unit 401 may comprise any suitable computational unitsuch as but mot limited to a microprocessor, FPGA (Field ProgrammableGate Array), ASIC (Application Specific Integrated Circuit), or similarunits. The mobile station comprises at least one memory 402 of volatileand/or non-volatile type. The memory may be for instance a RAM, DRAM,ROM, EEPROM, Flash memory, hard disk, and so on as understood by theskilled person. The communication interface may be any suitable asdiscussed earlier using a code division protocol.

In the solution, the BS device 5 has functionality for detecting andunderstanding these emergency or priority multiple-access sequences.Such a device 500 is shown in FIG. 5. The device 500 comprises also aprocessing unit 501, at least one memory 502, and an interconnectioninterface 503 for connecting to other components (not shown) of the BS5. Furthermore, the device 500 may comprise a downlink communicationinterface 504 and an uplink communication interface 505. The downlinkcommunication interface is arranged to communicate with the mobilestations (directly or indirectly using further downstream infrastructuredevices (not shown)) and the uplink interface 505 is arranged tocommunicate with the communication network. The downlink and uplinkcommunication interfaces may be built into the same physical interfacein some application configurations.

It should be noted that with the term base station is meant an entitythat receives or transmits wireless communication between wirelessterminals and a communication network. This may include for instance abase station in cellular mobile phone networks, an access point orgateway in a Wireless Local Area Network (WLAN), or similar networkaccess gateway devices.

It should be noted that the word “comprising” does not exclude thepresence of other elements or steps than those listed and the words “a”or “an” preceding an element do not exclude the presence of a pluralityof such elements. It should further be noted that any reference signs donot limit the scope of the claims, and that several “means”, “units” or“devices” may be represented by the same item of hardware, and that atleast part of the invention may be implemented in either hardware orsoftware.

The above mentioned and described embodiments are only given as examplesand should not be limiting to the present invention. Other solutions,uses, objectives, and functions within the scope of the invention asclaimed in the below described patent claims should be apparent for theperson skilled in the art.

Definitions and Abbreviations

-   ASN-GW Access service network gateway-   BS Base Station-   BSC Base station controller-   BW Bandwidth-   CDMA Code division multiple access-   DSA Dynamic Service flow Addition-   DSC Dynamic Service flow Change-   IEEE Institute of Electrical and Electronics Engineers-   NW Network-   OFDMA Orthogonal frequency division multiple access-   PKM Privacy Key Management-   QoS Quality of service-   REG Registration-   REQ Request-   RNC Radio network controller-   RNG Ranging-   RSP Response-   SBC SS Basic Capabilities-   SS Subscriber Station-   TLV Type, Length, Value-   UL Uplink

The invention claimed is:
 1. A method of handling emergencycommunication between a mobile station (MS) and a base station (BS),comprising the steps of: determining, by the MS, that an emergencycommunication is needed; initiating, by the MS, an emergencycommunication link with the BS; if the MS is not registered with the BS:obtaining specific emergency communication establishment sequences;using the specific emergency communication establishment sequences tonegotiate access to the BS and request emergency bandwidth; if the MS isregistered with the BS, but has not been granted bandwidth: using thespecific emergency communication establishment sequences to requestemergency bandwidth; and if the MS is registered with the BS and hasbeen granted bandwidth: sending an indication that emergency access isneeded in an identification message, and wherein the sequences are alsoused as communication division codes.
 2. The method according to claim1, wherein specific Code Division Multiple Access (COMA) codes are usedto indicate emergency access is needed.
 3. The method according to claim1, wherein specific random access preamble sequences are used toindicate emergency access is needed.
 4. The method according to claim 1further comprising a step of receiving emergency sequences from the BS.5. The method according to claim 1, further comprising a step of readingstored pre-set emergency sequences in the MS.
 6. The method according toclaim 1, wherein the step of obtaining emergency sequences comprises astep of choosing the sequence randomly from a set of available emergencysequences.
 7. The method according to claim 1, wherein the step of usingthe sequences to negotiate access is performed during initial accessestablishment.
 8. The method according to claim 1, wherein the step ofusing the sequences to negotiate access is performed during bandwidthestablishment.
 9. A mobile station (MS) for a wireless communicationnetwork, comprising: a transceiver for wireless communication with abase station (BS); a processor arranged to execute functions for:determining that an emergency communication is needed; initiating anemergency communication link with the BS; if the MS is not registeredwith the BS: obtaining specific emergency communication establishmentsequences; using the specific emergency communication establishmentsequences to negotiate access to the BS and request emergency bandwidth;if the MS is registered with the BS, but has not been granted bandwidth:using the specific emergency communication establishment sequences torequest emergency bandwidth; and if the MS is registered with the BS andhas been granted bandwidth: sending an indication that emergency accessis needed in an identification message, and wherein the sequences arealso used as communication division codes.
 10. A base station (BS) forwireless communication with a mobile station (MS) comprising: aprocessor arranged to execute functions for: if the MS is not registeredwith the BS, detecting communication establishment sequences from theMS; if the MS is registered with the BS, but the BS has not grantedbandwidth, identifying specific emergency sequences from theestablishment sequences, the specific emergency sequences used torequest emergency bandwidth; handling emergency communication; and ifthe MS is registered with the BS and the BS has granted bandwidth,sending a second indication of emergency access in an identificationmessage, wherein the sequences are also used as communication divisioncodes.
 11. A non-transitory computer-readable medium for a mobilestation (MS) programmed with instruction sets operable when executed bya computer processor of the MS, for: controlling wireless communicationwith a base station (BS); determining that an emergency communication isneeded; initiating an emergency communication link with the BS; if theMS is not registered with the BS: obtaining specific emergencycommunication establishment sequences; using the specific emergencycommunication establishment sequences to negotiate access to the BS andrequest emergency bandwidth; if the MS is registered with the BS, buthas not been granted bandwidth: using the specific emergencycommunication establishment sequences to request emergency bandwidth;and if the MS is registered with the BS and has been granted bandwidth:sending an indication that emergency access is needed in anidentification message, and wherein the sequences are also used ascommunication division codes.